1. Field of the Invention
The invention relates to a sun protection installation.
2. Prior Art
From DE 42 39 003 A1, sun protection lamellae have been known which have a toothed underside and a stepped upper side. The step-shaped upper side is arranged like a staircase so that on the irradiation side of the lamella the sun light incides in principle on the treadboard and the riser, i.e. the whole first portion of the lamella surface is exposed to sun irradiation. This is also the case if the lamella is arched as a whole or sun irradiation penetrates at a high, or flat, respectively, angle of incidence on the lamella.
In DE 44 42 870 A1, sun protection lamellae have been shown comprising two portions, a first step-shaped portion and a second portion. The step-shaped portion is so shaped that light is primarily reflected back into the outer space by two reflections on the upper side of a lamella in that the light is reflected from the treadboard onto the riser, or from the riser onto the treadboard, respectively. Treadboard and riser are exposed to direct sun irradiation.
The disadvantage of this design is an undesirable heating up at the lamella and hence of the interior space since each reflection process is accompanied by a certain absorption. Particularly in the case of interior venetian blinds comprising lamellae, such multiple reflection should be avoided, because it leads to unnecessary heating up and thermal stress of the interior space.
A further problem consists in that this lamella cannot be compacted to vertically suspended lamella packages. While the lamella may be laid one into the other, they slide to the side because of the essentially vertically arranged risers. The disadvantage is that these lamella packages cannot be slid into a venetian-blind chute.
A further disadvantage is that because of the inciding sun, even in case of geometrically correct design of the light deflection on the riser, a glare effect occurs when looking on the venetian blind lamelia from above, as is for instance the case when standing behind a lamella curtain in the interior space. Small unevennesses in the reflective surface namely lead to light scattering or an undefined light deflection to the interior space which is experienced as a glare.
It is therefore the aim of the present invention to develop a sun protection installation comprising reflective lamellae having a step-shaped surface which can reflect sun irradiation, at least for high angles of incidence, by one single reflection again into the outer space while in case of flat angles of incidence, illumination of the space depth is possible as well. A further aim is to provide a reflective lamella which does not lead to glare effects in the interior nor in the outer space.
This problem is solved in accordance with the present invention.
The advantage of the invention lies in the optical heat regulation by the formation according to he invention of the teeth of the first portions in favour of thermal comfort and in the formation according to the invention of the second portions in favour of visual comfort in the interior space. The teeth include a sun-irradiated side and a shaded side. The high overheating summer sun incides on the sun-irradiated side and, apart from a few exceptions, is reflected therefrom by one single reflection into the outer space. To this end, the tooth angles xcex11 within the first portions should be shaped preferably  greater than 30xc2x0 increasing relative to the second portion. For the critical high positions of the sun, it can thereby be avoided that the light irradiation on the upper side of a lamella is subjected to double reflection. More flatly inciding sun is also subjected, primarily in winter, to a second or further reflections, however on the underside of the upper lamella. By a defined angle of impact xcex11 of the irradiated tooth sides relative to the horizontal H, the process or the timing of the deflection of the sun light, i.e. the optical behaviour of the lamella, can exactly be defined.
A further advantage of the invention is to be seen in the freedom from glare of the sun protection lamella. In accordance with the invention, the tooth side facing the sun light takes a deflecting function, the tooth side facing the interior space takes a dimming function. From the interior space, at least in the first portion, it is namely not the irradiated side but rather the shaded side of the teeth which is visible. The latter becomes darker and is glare-free since it is irradiated by sun light only immaterially, if at all. With a view to this property, it is possible to provide the lamella either with a reflective surface or with a white or diffuse surface while no glare effect occurs when looking at the lamella. Glare in the outer space, for instance in an opposite building, is avoided in particular because of the different angles of inclination xcex11 and/or by an arched tooth shape of the sun-irradiated upper sides of the teeth since light deflection occurs diffusely. Second and/or further portions, because of the more flat angle of impact xcex11 of the sun-irradiated tooth sides, take charge of a light deflection function to the interior space. Preferably, the angles xcex11 are selected xcex11 greater than 0 and more flat than in the first portion. One exception from the rule may be the starting point of the second portion following the first portion. It may be inclined towards the interior space so that the light is deflected in a very flat way to the interior space.
The sun protection lamella is also arranged as a venetian blind behind a glazing in the interior. With a view to metal oxide coverings, particularly sun protection and heat protection glazings show an increased reflection of the incident light radiation. As a result of retro-reflection of the first portion, reflections of the retro-reflected light radiation on the inner side of the glazings occur. These reflection provoke a glare in the interior space since the sun light is reflected from the glass into the observer""s eye. By the different angles of impact xcex11 of the individual teeth relative to the horizontal in the first portion of the lamellae, this glare is considerably reduced since retro-reflection is scattered and is reflected, with increasing distance from the inner faxc3xa7ade, over a larger field of vision. A major part of the reflected retro-reflection is also absorbed by the scattering on the undersides of the upper lamellae. Thereby, too, the glare into the observer""s eye is reduced (FIG. 4).
The advantage of the toothed surfaces is particularly to be seen in that the lamella leaf may be arranged in a horizontal position so that good transparency and diffuse light entrance between the lamellae arranged in opened position is safeguarded while, nevertheless, direct sun is deflected out. Would one try to obtain the same optical effect of light deflection by means of a commercially available venetian blind, the lamellae would at least have to be positioned at an angle xcex11 resulting in that the venetian blind would become intransparent and diffuse light entrance into the interior would be prevented. This common lamella position is for instance shown by dash-dotted line 32 of FIG. 1. The lamella according to the invention is suited for stationarily fixed sun protection installations, for instance also in the shape of a single lamella. In case of rotatable suspension of the sun protection lamellae, for instance in the shape of a venetian blind, the lamella leaf may, in case of high-inciding sun in summer, even be bent inwardly (FIG. 5) so that out-reflection of direct radiation incidence and shading of the interior space occurs, a particularly high permeability for diffuse sun radiation and an even improved transparency of the lamella curtain, however, is safeguarded. This is desirable in order not to darken the interior in spite of the shading. In this way, the lamella may also be continued towards the interior space with a plurality of portions which effect aimed light incidence either into the depth of the interior space or to the interior space ceiling.
Under first portion, one should understand in principle that first portion having a toothed upper side by which in the normal position sun incidence can be back-reflected to the sky by one single reflection. Under further portions, one should understand those lamella portions by which light radiation can be reflected, preferably by one single, or a plurality of, reflections, into the interior space. Under normal position, one should understand a starting angular position of the lamellae for which they are calculated. When pivoting the lamella into a different position, light guiding effects and angular data different from those of the description for the normal position may occur. Usually, the normal position refers to a lamella angular position of from 0-30xc2x0 to the sun whereby the angular position is determined by a centre line through the lamella relative to the horizontal. However, different lamella position angles are possible as well.
Further advantages will be explained based on the drawings of advantageous embodiment variants.